def self.authenticate(username="", password="")
      ldap_con.auth auth_string, password

      if rs = ldap_con.bind_as(
                :base => base,
                :filter => email_filter,
                :password => password)
        user = User.new
        user.logged_in=true
        user.name = username
        user.ldap = rs[0].to_hash
        return user
      else
        return nil
      end
end